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Doppler and the Big Bang Theory. (Scientific).
This "redshift" indicated that Sirius was moving away from us. A few years later he was able to calculate the radial velocity of the star Sirius at between 26 to 36 miles per second.
During the 1890's the Lick Observatory in California began to track and chart the radial velocity which is actually the velocity at which the line of sight that the star is observed of many stars, as well as gaseous and planetary nebulae. Astronomers at Lick calculated the measurements of 400 stars including their radial speed and velocity.
In 1910 Vesto Slipher measured the velocity of the Andromeda Nebula at 300 km per second, thirty times greater than previously observed. Four years later, Slipher had confirmed the radial velocities of 14 spiral nebula, with the overwhelming majority shifting to the red end of the spectrum. Slipper's observations showed that the majority of spirals he measured were moving away from us.
Around 1913 several astronomers, among them Edwin Hubble, used a variable star known as a Cepheid a star that fluctuates in intensity to measure their period-luminosity relationship. This would accurately determine the distance to any Cepheid in the observable vicinity.
Hubble became the first Astronomer to discover an independent Galaxy outside the confines of the Milky Way. Hubble calculated the distance of the Andromeda Galaxy to be 900,000 light years away; larger than the predicted size of our own galaxy. Using the radial velocity measurements of Slipher along with Hubble's own calculations he began to notice a correlation between the distance of these Galaxies and their radial velocities.
The proof was conclusive: the further away a Galaxy was relative to the Earth, the greater the velocity of that galaxy. Hubble had irrefutable proof that the universe was expanding. By 1936 Hubble had received data from Galaxies more than 100 million light years away. The redshifts at this distance were so large that the spectral lines had changed color.
As Astronomers were collecting data on the universe based on their observations, theorists were busy developing models that attempted to explain the cosmos. Recently equipped with Albert Einstien's theory of Relativity, Einstein was one of the first to attempt an explanation of the physical Universe. Einstein believed the universe to have a static, uniform, isotropic distribution of matter.
Einstein's calculations however proved to result in the exact opposite, an oscillating universe that had the potential for expansion or contraction. He was certain that the universe was stable. Einstein was compelled to amend his original equation. He used the term cosmological constant, which created a spherical, four-dimensional closed universe.
Around the same time the Dutch Astronomer Willem deSitter used Einstein's general theory of relativity to develop his own model of the Universe. His model was unique in that it did not take into consideration the existence of matter in the Universe. However it did go beyond Einstein's model in that it predicted the redshift, even though de Sitter felt it was an illusion, and did not at the time link it to any recession of celestial objects.
The academic community of 1930 did not fully embrace either model of the universe. Then the Secretary of the Royal Astronomical Society in England was made aware that three years previous, one of his students had written a theory of the universe independent of the two major forces in cosmological theory. Georges Lemaître created a cosmology that predicted a universe that was forever in a state of expansion.
When this theory was rejuvenated by its republication in the journal Monthly Notices, it brought to the table another similar theory that was devised ten years earlier. Aleksander Friedmann, a Russian mathematician, analyzed Einstein's cosmological constant that produced a static universe. Friedmann proved that there are three possibilities for the universe when the cosmological constant is zero. If the matter in the universe is greater than the critical density, the universe would ultimately collapse back onto itself.
If the inverse is correct the universe would expand forever. If the universe were flat with a constant of zero at critical density, the universe would again expand infinitely. Both Lemaître and Friedmann's solutions were analyzed by Einstein and were summarily dismissed. It was not until Hubble had proved that Galaxies were in fact receding in 1932 that Einstein was forced to drop his static universe model. The observational proof that the universe was expanding, combined with the models of Friedmann and Lemaître that predicted an expanding universe unified the cosmologist and the astronomer in agreement.
The only question remained was if the universe is expanding, what was the origination of this expansion? Lemaître used the second law of thermodynamics as his starting point. Based on the assumption that the expansion of the universe was an increase in the disorder of a system, originating from a singularity of neutrons, this primordial nucleus would then explode where an increase in the entropy of the universe would be apparent. On May 9, 1931, Lemaître published his theory of the universe in the journal nature and it was met with general skepticism.
George Gamow expounded on Lemaître's work, using recent discoveries in quantum theory. Lemaître formulated his model based on the theory that a giant nucleus began to entropy, breaking down into individual constituents. Gamow believed that a nucleus containing not only Neutrons but protons and electrons as well was the starting point. Fred Hoyle Big Bang.
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